Senjo H, et al. - In 64 patients with diffuse large B-cell lymphoma (DLBCL), researchers investigated whether and to what extent serum levels of soluble interleukin-2 receptor (sIL-2R) correlated with total metabolic tumor volume (TMTV). The ultimate goal was to explore a surrogate marker for TMTV given that high cost and poor access to the imaging facilities hamper wider use of ¹⁸F-FDG PET/CT to calculate TMTV. Findings revealed a significant correlation between serum levels of sIL-2R and TMTV. Failure to achieve 2-year EFS (EFS24) was predicted by the cutoff value of TMTV ≥150 cm³ or sIL-2R ≥ 1300 U/mL, in receiver operating curve (ROC) analysis, with areas under the curve (AUC) 0.706 and 0.758, respectively. Worse 5-year overall survival and event-free survival was reported in significant relation to each of TMTV ≥150 cm³ and sIL-2R ≥1300 U/mL. Among NCCN-IPI (National Comprehensive Cancer Network-International Prognostic Index) high-intermediate and high-risk group, patients with favorable prognosis were detected by each of sIL-2R <1300 U/mL or TMTV <150 cm³. Overall, serum level of sIL-2R can be conveniently used in place of ¹⁸F-FDG PET/CT to estimate metabolic tumor burden.